JPS62257054A - Apparatus for measuring moisture of particulate material - Google Patents

Abstract

PURPOSE:To detect water content by erasing the flow amount of a specimen, by connecting two resonance circuits having resonance frequencies different from applied frequency and different from each other to the same oscillation circuit in different degrees of coupling. CONSTITUTION:Electrodes P1, P2 are opposed to constitute a measuring condenser Cd1 and electrodes P3, P4 are opposed to constitute a measuring condenser Cd2 and the electrodes P1-P4 are alternately arranged along the circumference of a circle to constitute a cylindrical body and a particulate material is allowed to fall in said cylindrical body to flow therethrough. The output of an oscillator OSC is connected to two resonance circuits L1, L3 through a change-over switch SW in different degrees of coupling so as to be change over. One of both resonance circuits contains the condenser Cd1 and the other one contains the condenser Cd2 to make the resonance frequencies of both resonance circuits different. By this constitution, the changes in the capacities of two sets of the condensers Cd1, Cd2 at the time when the cylindrical body is empty and at the time when a specimen passes therethrough are detected.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an apparatus for continuously measuring the water content of powder or granular materials using high frequency waves.

The conventional technique for measuring the water content of powder and granular materials is to measure a sample of a constant weight by
``eMI The basic method is to use the ``eMI'' method to break tongues and bribes, but this method does not allow continuous measurement and is time-consuming, so continuous monitoring of materials and products on the production line is not recommended. cannot be applied to

Compared to ordinary insulating substances, water has a large dielectric constant even at the poles.
Since it has considerable electrical conductivity, various methods for electrically measuring water content have been proposed. One of the principles of this method is to utilize the fact that there is a certain relationship between the change in the capacitance of a capacitor and the water content when a sample is placed between the electrodes of the capacitor. As means for measuring the change, methods such as creating a resonant circuit and measuring the change in the resonant frequency, configuring an AC bridge and directly measuring the change in capacitance, etc. are used.

As an apparatus for continuously measuring the moisture content of powder or granular materials using the above-mentioned electrical method, an apparatus having a configuration as shown in FIG. 4 is conventionally known. In this figure, PL and P2 constitute a capacitor with opposing electrodes, and are connected to the capacitance measuring means I.
Electrode P1. During P2, the powder sample S is continuously mixed τ
71] - The sample falling between P1 and P22 passes through the powder flow meter V and flows to other processes. Changes in the capacitance of the capacitor constituted by PL and P2 are determined by the amount of sample present between the two electrodes and the water content, and the amount of sample present between the electrodes is proportional to the flow MF of the sample. Therefore, when the capacitance change is ΔC1 and the water content is W, generally kΔC
=Ff(W)...The relationship (1) holds true. child\
k is a constant determined by the electrode shape of the capacitor composed of electrodes Pi and P2, and the functional form of f (W) varies depending on the properties of the powder and the frequency used to measure the capacitance of the capacitor, but depending on the sample and frequency. If is fixed, it is a constant function. However, in this method, it is necessary to know the flow rate F in order to determine the water content W, and therefore a powder flow meter V is used. Therefore, a method as shown in FIG. 5 is known as a method that does not require a powder flow meter. This method uses two capacitors shown in Figure 4 arranged one above the other.
pl and P2 constitute one capacitor Cdl, and PL'
, P2' constitute another capacitor/Cd2, and the high frequency frequencies applied to each capacitance change are different. Capacitor cd1. If the capacitance changes of cd2 are ΔC1 and ΔC2, then kl·ΔC1=Ff (W, fl) k2·ΔC2=F t (W, f 2 ). Here fl and f2 are capacitor Cdl.

This is the frequency of the high frequency applied to Cd2.

When the powder flow rate F is eliminated from the above two equations, Pl.

The water content W can be determined from the electrode shapes of the pair P2 and the pair P1 and P2. However, this method does not require the granular material flowmeter V, but requires two oscillators for each of the frequencies fl and f2, and since two capacitors, which are measurement electrodes, are arranged one above the other, the device does not need to be placed on the back. The value will be high.

Problems to be Solved by the Invention The present invention attempts to solve the problems that the method shown in FIG. 5 requires two oscillators with different frequencies and that the height of the device increases. .

D0 Means for solving the problem Divide the cylindrical body into four parts along the axial cut, use each of the four parts as a measuring electrode, and configure two capacitors with each pair of opposing parts. The sample powder is allowed to fall in the axial direction inside the cylindrical body. On the other hand, the output of one oscillator is selectively connected to two resonant circuits with different degrees of coupling via a changeover switch. One of these two resonance circuits includes one of the two sets of capacitors, and the other includes the other of the two sets of capacitors, so that the resonance frequencies of the two resonance circuits are different (such a configuration The change in capacitance of the two sets of capacitors is detected when the inside of the cylindrical body is empty and when a sample is passing through it.The means for detecting the change in capacitance is arbitrary, and the change in the resonant frequency due to the change in capacitance is Alternatively, the resonant frequency may be fixed at the resonant frequency when the capacitor is empty, and a change in the detection output may be detected.

Ho0 effect Two resonant circuits are connected to the same oscillation circuit with different degrees of coupling,
In addition, if the respective resonant frequencies are different from the applied frequencies, and if they are also different from each other, the response characteristics of the two common imaging circuits to changes in the capacitance to be measured connected to the resonant circuit will be different, resulting in an appropriate response. For example, by taking the ratio of the voltage across the capacitance to be measured, the flow rate of the sample can be eliminated and the water content can be detected. , the height of the device can be reduced.

Embodiment FIG. 1 shows the electrode arrangement of two capacitors in an embodiment of the present invention, in which PI and P2 face each other to constitute one measuring capacitor Cdl, and P3 and P4 constitute one measuring capacitor Cdl. The capacitors t4 and t4 are arranged opposite to each other at right angles to form another measurement capacitor Cd2, and the capacitors t4P1 to P4 are arranged alternately along the circumference to form a cylindrical body, and the capacitors t4 and t4 are arranged alternately along the circumference to form a cylindrical body. is caused to fall and flow through this cylindrical body from top to bottom.

FIG. 2 shows a circuit of one embodiment of the present invention. O3C is an oscillator that outputs a high frequency wave with a constant frequency. Let the frequency be fO. Ll and L3 are first resonant circuits, both of which are tuned to the oscillation frequency fO of the oscillator ○SC, and the output of O20 is applied alternately by a changeover switch Sw.

L2. L4 is a second resonant circuit, L2 is connected in parallel to Ll via a coupling capacitor C1, L4 is also connected in parallel to L3 via a coupling capacitor C2,
The resonant frequencies of these resonant circuits are different from fo and also different from each other. Also, the capacitances of the coupling capacitors CI and C2 are different from each other, for example, CI=10pF, C2=100
pF is selected. The measurement capacitor Cdl is connected in parallel to the resonant circuit L2, and Cd2 is connected in parallel to the resonant circuit L4. DETl and DET2 are both detection circuits,
Resonant circuit L2. L4, and their respective outputs are input to the data processing circuit DIG.

Before explaining the configuration and operation of the data processing circuit DIG, the operation of the above-mentioned circuit will be explained with reference to FIG. FIG. 3 shows the detection circuit DET1. D.E.
The change in the output voltage of T2 is expressed using the output frequency of the oscillator osc as a parameter. That is, the output voltage of each detection circuit when there is no sample is Vd1. Vd2. When the output voltages when the sample is passing through are Vl and V2, the third
Figure A shows the output of the detection circuit DETI, and the vertical axis C (V (1
1-'v' 1) / V d 1 and the same B HaD
E The vertical axis shows the output of T2 (Vd2-V2)/Vd
It is 2. The resonant frequency of the resonant circuit L2 is fo-A-fl
The resonant frequency of H,,1,4 is f o -1'r2 Hz
and f'o is varied in the range from 37.2 KHz to 8.10 MHz. As is clear from the figure, r)' E-, T
The change in the output of No. 1 due to the water content is 2.76 MF (it is linear in a wide range near z, and if fo is too high or too low, the rate of change decreases and the value linearity becomes poor (the capacitance of the coupling capacitor C1 The output of DETI with a smaller value changes less depending on the water content at any frequency.The reason for this is thought to be as follows.The capacitor Cd composed of electrodes P1 to P4
The capacitance of Cd2 is about 2 pF when empty, and 2 pF when there is a sample.
~200 pF. Resonant circuit L2. L4 has such a capacitor Cd1. Since Cd2 are connected in parallel, their resonant frequency is Cd1. The frequency is further shifted to the lower frequency side than when Cd2 is not present, and the resonant circuits L2 and L4 act as capacitive actances with respect to the input frequency fo. And in the C2, L4, and DET2 systems, C2
Since the reactance of the resonant circuit L4 and the reactance of the resonant circuit L4 described above are approximately the same, the influence of the change in Cd2 appears greatly. On the other hand, C1, L2. In the DETI system, since the capacitance of C1 is small, a voltage close to the voltage across the resonant circuit L1 appears in DETl, making it insensitive to changes in Cd1. When the moisture content of the sample is W1 and the flow rate of the sample is F, the equation of the curve in Figure 3 at unit flow rate is given. )V
It is expressed as C2=F-K(W)-(4). This is because in a powder sample, the amount of N water has a much greater influence than the powder itself. Above (3)
<4') From the formula, Ve 1/Ve2=H(W)/K
By (W)-(5), the flow iF can be eliminated and W can be found. There is no need to specifically find the functional form H, 4! What is necessary is to prepare a y quasi-sample and measure the correlation curve between Vel/Ve2 and W.

According to the above, in this example, fo is 2.7
6MHz is used. Returning to FIG. 2, the configuration and operation of the data processing circuit DIG will be explained.

5UT11.5UB2 is a subtraction circuit. Switch Sl
, S2 are interlocked, and when the sample is not passed through the electrodes P1 to P4, SL and S2 are connected to the terminals bl and b2 of 5UB1.5UB2, and the second detection circuit DET1 is connected.
．． The outputs Vdl, Vd2 of DET2 are held in the storage capacitor Cm. Next, 5UB1.5U of Sl and S2
One terminal a1 of B2. Switch to the a2 side and connect the electrodes P1 to P4.
Pass the sample through the tube. Then, since Vd1-VL and Vd2-V2 appear on the output sides of 5UBI and 5UB2, these are input to the division circuit RA, and the division result is displayed as the water content on the display device DsP. In this operation, Vd2/Vd1 included in the equation (5) is not included, but since this becomes a constant of the device, it is not necessary to take it into account when determining the moisture content through calibration.

Effects of the present invention In the above-mentioned calibration, the two sets of measuring electrodes are arranged in a cylindrical shape at the same height to form two capacitors, so the height of the device can be reduced and the device can be made portable. It can be installed in a narrow place on a production line, and since only one oscillator is required, it is inexpensive, and the frequency error is much smaller than the influence of two frequency errors that occur when two oscillators are used. The impact of

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the arrangement of measurement electrodes in the present invention;
Fig. 2: A circuit diagram of an embodiment of the present invention; Fig. 3 is a graph explaining the operation of the device of the embodiment;
2. Action graph of the DETI strain, B is C2, L4. D
FIG. 4 is a side view of one conventional example, and FIG. 5 is a side view of another conventional example.

Claims (1)

[Claims] Two resonant circuits with different resonance frequencies are coupled to one oscillation circuit with different degrees of coupling, and four measurement electrodes are arranged in a cylindrical shape.
The sample is configured to pass through it, and each pair of the four measuring electrodes facing each other constitutes a capacitor, one of which is connected to one of the two resonant circuits, and the other is connected to the other. A powder moisture measuring device that is connected to a resonant circuit and calculates the moisture content from the ratio of the detected output of the voltage across these two capacitors.